GameChief and Isonyx are both right. Adding to that, it also depends on HOW MUCH DATA you have to sort. For example, Google has to sort A LOT of data. They use a combination of sorting algorithms and parallel processing in order to be able to handle the data. I'm also pretty sure they use custom hardware optimized to sort data efficiently (as in power consumption and sorting speed, etc.).

If you had 10 bytes of data to sort, then you can pretty much do whatever you want to sort it (except BogoSort and stuff like that).